Abstract

Antireflective subwavelength structures (ARS) resembling nanostructures found on the cornea of night-active insects reduce the reflection of light by providing a gradual change in the refractive index at the interface. These artificial ARS have mainly been fabricated by a combination of conventional lithography and reactive ion etching, which constrains their application to planar substrates. We report on the fabrication of ARS using three different techniques including bottom-up and top-down methods as well as their combination on microlens arrays (MLAs) made of fused silica. The optical performance of the resulting ARS on the MLAs is as good as ARS fabricated on planar substrates with increased transmission of up to 96% at certain wavelengths.

Figures (7)

Interference microscopic images of the investigated MLAs. Left, MLA with a periodicity of 50 µm; center, MLA with a periodicity of 500 µm; and right, array of cylindrical lenses (periodicity, 100 µm). The structure height is 5 µm for all arrays.

Transmission spectra of different MLAs equipped with ARS, which have been fabricated a) by a combination of BCML and RIE and b) by stochastic RIE process. From light to dark: planar substrate, cylindrical MLA, 50 µm MLA, and 500 µm MLA. Dotted curves show the transmission of a second set of AR surfaces on MLAs with 500 µm pitch.